Fuel economy

3998 Views 62 Replies 13 Participants Last post by peter47, 24 d ago

peter47

Discussion Starter · 5 mo ago

Somewhere way back, SCHS posted about finding quite a discrepancy between the car's claimed average fuel consumption, and what he found by actual measurement. I found this a bit of a challenge, so started doing the same. Thus far, over just two tank fill-ups to the kick-off point, zeroing the trip meter each time, mine has averaged out at an actual 9.2 L/100Km, against the car computer's claim of 8.2 L/100Km.

Now while not spot on, I never expected it would be, but it's not too bad if it is only optimistic to the tune of 1 extra litre of fuel consumed over 100km..?
However, to be fair, I also do a lot of shortish trips and most of my distance covered is on roads with speed zones between 40kph and 80kph, with lots of roundabouts, and we only occasionally get off the island and onto freeway type roads of up to 110kph. So I wasn't expecting spectacular figures. Anyone else checked..? SCHS, any further progress figures..?

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iminhell

· #2 · 5 mo ago

In freedom units,
9.2 = 25.5MPG
8.2 = 28.5MPG

With mine I've found short trips really do kill MPG's. It takes quite a bit of steady state highway driving to overcome a few short trips. Kinda makes a guy wonder what lean burn programming is going on in the cars brain.

Futures trader

· #3 · 5 mo ago

My dash display says I’m getting 31 mpg but I’m only getting 24.

Reactions: 1

peter47

Discussion Starter · #4 · 5 mo ago

Futures trader said:
My dash display says I’m getting 31 mpg but I’m only getting 24.

One suspects the car economy computation, however it's done, is set up to be...let's just say...optimistic..? A bit like the speedo reading. Do you folk have an inbuilt over-read in the speed indication. Here in Aus they seem to have been programmed to over-read by 4kph, no matter what the speed, so it's not simply a percentage error. That is at 100kph you are actually, by GPS, doing only 96. Same 4kph difference right through the speed range..? I might start a new thread on this. I think Speedtek has indicated something similar in the Canadian models..?

197

· #5 · 5 mo ago

Being in USA I have checked mine on a regular basis. It's usually off by 1 or 1.5 mpg. I ignore the real time mpg and only pay attention to the overall average. I do a lot of highway driving so with my SX I'm averaging about 30-31mpg, which I'm very happy with it being an Allwheel drive small suv.

Reactions: 1

ta2102

· #6 · 5 mo ago

NumbNuts said:
Being in USA I have checked mine on a regular basis. It's usually off by 1 or 1.5 mpg. I ignore the real time mpg and only pay attention to the overall average. I do a lot of highway driving so with my SX I'm averaging about 30-31mpg, which I'm very happy with it being an Allwheel drive small suv.

I'm averaging the same, roughly. But I'm not an AWD so maybe I should be a little less heavy on the pedal. It's anywhere from 29-32mpg on the longterm averages.

Reactions: 1

iminhell

· #7 · 4 mo ago

So where is the car grabbing speed from? is it the same place as the miles? Presumably it is. It might be from the wheel speed sensors or it could be from a VSS in the transmission ... and which transmission do you have, CVT or DCT?

But if the speed is off it's a safe bet the fuel economy calculation is also off (by the same factor). I'm not going to go through and do the math.

Fogwash HT

· #8 · 4 mo ago (Edited)

It's time for me to do some manual calculations as my 23 LX AWD is reading an average accumulated mpg of 34 with some trips being as high as 40. I cannot tell if I am in the goldilocks zone of trip length and speed, am a gentle driver, the number is off, or it's just great gas mileage.

peter47

Discussion Starter · #9 · 4 mo ago

Fogwash HT said:
It's time for me to do some manual calculations as my 23 LX is reading an average accumulated mpg of 34 with some trips being as high as 40. I cannot tell if I am in the goldilocks zone of trip length and speed, am a gentle driver, the number is off, or it's just great gas mileage.

Then there's no avoiding it. You need to tank up to the kick-off - zero the trip meter - you can't loose the overall distance reading, so relax - just hit and hold the 'ok' button on the wheel a second or two - then tank up and take trip reading again when nearly empty - do this several times, then average out doing the maths. Let us know what you find.

Reactions: 1

Speedtek22

· #10 · 4 mo ago

Road Trip is an excellent app for the iPhone, I’ve been using it for years…I don’t know if they have an android version.

‎Road Trip HD

‎Road Trip HD is the fastest and easiest app for tracking of your car’s fuel economy, maintenance history, and expenses. Remember to checkout Road Trip Lite and Road Trip for the iPhone. _____________________________ "There’s a ton of MPG apps on the App Store but Road Trip is the best...

apps.apple.com

iminhell

· #11 · 4 mo ago

E50 average MPG is 18.7 combined.
Just throwing that out there. LOL

Bloo

· #12 · 4 mo ago

My lifetime Fuelly mileage is still above 32mpg. However, it's dropping fast with the winter gasoline formulation here in New England. Winter fuel sucks sweaty bull nuts.

The 2.0 engine is very sensitive to fuel and ambient temp. The modified Atkinson design squeezes most of the thermal energy from each combustion cycle. The result is that combustion chamber pressure is about equal to atmospheric pressure when the exhaust valve opens.

As ambient temperature drops, there is less "thermal overhead" to work with. Winter fuel typically also has a lower energy content due to additives that prevent freezing and ensure combustion at low temperatures. This one-two punch reduces available power, so you have to push the go pedal a bit harder for the same result. We pay for that result with lower fuel economy. My car sees more than a 5mpg difference between summer and winter driving.

The higher thermal efficiency means a cooler running engine during the summer. Unfortunately, waste heat is something you want in winter. If your Seltos sometimes leaves you with cold feet, blame Atkinson.

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peter47

Discussion Starter · #13 · 4 mo ago

That's very interesting. Thanks for that, Bloo.

Reactions: 1

SHCS

· #14 · 4 mo ago

Bloo said:
My lifetime Fuelly mileage is still above 32mpg.

I'm curious how you've determined your lifetime fuel economy. Are you looking at fuel purchase vs distance? Or are you relying on the numbers on your trip meter?

Bloo

· #15 · 4 mo ago

SHCS said:
I'm curious how you've determined your lifetime fuel economy. Are you looking at fuel purchase vs distance? Or are you relying on the numbers on your trip meter?

The Seltos MPG computer drinks bong water. It's wildly optimistic - typically returning 10% above actual. To me, "actual" is determined at every fuel fillup using "miles_driven / gallons_filled". I enter the numbers on Fuelly. Bloo has used 1522 gallons over 49,778 miles for a lifetime 32.7mpg.

I filled up my tank today. Brainiac returned 33.5mpg. Actual was 30.4mpg.

The best mileage I ever got was 40.1mpg. However, Brainiac insisted it was 44.5mpg. I drove 505 miles on that tank. Anyhoo...that has to be a record for a Seltos.

peter47

Discussion Starter · #16 · 4 mo ago

Good info Bloo. I'm also, by doing the top-up/distance calc each time I now fill, am finding the car computer computation is...shall we say...somewhat optimistic..? Having said that, it's not too far out, so is a guide, if you allow for the 10% optimism..?

Reactions: 1

nuclearlemon

· #17 · 4 mo ago

for those that have bought new, did you find it didn't get good mileage right off the bat, but got better a tank or two in? also, has anyone compared "smart" mode vs. "normal" ?

i got my nightfall with 19 miles on the odo. first tank was only around 25/mpg using "smart" mode. i'm early on the second tank (been snowed in, so haven't been able to drive it for over a week) but in normal mode, i'm around 30. will be interesting to see where i am this time next year when the engine is broken in

ta2102

· #18 · 4 mo ago

Normal mode is the mode you want to be in for best mileage. Smart mode switches between normal and sport mode basically depending on how you press your gas pedal. You probably notice "smart" mode is a lot more jerkier of a drive. Also, a lot of people assume "smart" mode means eco or something but that's not the case at all.

Speedtek22

· #19 · 4 mo ago

ta2102 said:
Normal mode is the mode you want to be in for best mileage. Smart mode switches between normal and sport mode basically depending on how you press your gas pedal. You probably notice "smart" mode is a lot more jerkier of a drive. Also, a lot of people assume "smart" mode means eco or something but that's not the case at all.

Smart switches between Eco, Normal, and Sport as required...although here in North America we don't have a dedicated "eco" selection like they do in other markets.
One of the interesting reasons Sport reduces mileage (just noticed this the other day on the highway drive...I had 5 hours to kill) is the diff transfers some power to the rear wheels at all times, even when driving at constant highway speeds. Saw it on the driven wheels screen...rear wheels got two bars in sport at constant speed, all other modes had none.

nuclearlemon

· #20 · 4 mo ago

ta2102 said:
Normal mode is the mode you want to be in for best mileage. Smart mode switches between normal and sport mode basically depending on how you press your gas pedal. You probably notice "smart" mode is a lot more jerkier of a drive. Also, a lot of people assume "smart" mode means eco or something but that's not the case at all.

good to know...my salesman was new and he apparently didn't know that because he told me it was for fuel economy.

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